My issued U.S. Pat. No. 8,544,515 discloses lightweight wheels and runflat tires based upon negative Poisson's ratio (NPR) or auxetic structures. A wheel with NPR tire is called N-Wheel in this application, which is considered as an integrated product of traditional wheel (rim) and tire. The N-Wheels can be tailored and functionally-designed to optimally meet the various requirements for both military and commercial vehicles. N-Wheels may be fabricated using standard materials and simple manufacturing processes, resulting in low-cost and high-volume production. Among many other possibilities, the disclosed designs are two new evolutions of the original N-Wheel concept, with a number of following new features: 1) reflecting the practical manufacturability and fabrication issues; 2) reflecting assembly process with the consideration of mass production; 3) in the first design, the inner layer of the stuffers is integrated with the rim as one integrated part to be fabricated; 4) tendons (top layer of the nested V shapes in the NPR structure) are now formed by continuous belt-like material and each layer is separated as multiple specially-designed belts; and 5) with essential three-dimensional manufactural details. Note that the disclosed designs are readily utilizable or be modified for the wheels of forklifts, lawn mowers, recreation utility vehicles (RUV), and etc.
An auxetic wheel according to the '515 patent comprises a line defining an axis of rotation; and a plurality of concentric rings of unit cells surrounding the axis, each unit cell being constructed of a plurality of members defining a Negative Poisson's Ratio (NPR) structure. The outermost ring of unit cells is arranged to facilitate rolling terrain contact, such that the stiffness of the structure in the localized region of loading increases due to terrain contact increases as the wheel rotates.
A layer of material may be disposed between the concentric rings of unit cells which in preferred embodiments comprise a plurality of nested-V shapes. A cover may be provided over the outermost ring of unit cells forming a tire which may, or may not, be inflated.